Optimizing fixation methods for stable and unstable intertrochanteric hip fractures treated with sliding hip screw or cephalomedullary nailing: A comparative biomechanical and finite element analysis study.

BACKGROUND: Despite recent advances in implants and surgical techniques, catastrophic and clinical failures in the treatment of intertrochanteric fractures continue to occur, with dire consequences in an overall frail population subset. The aim of the current study is to evaluate the effect of the factors under the surgeons' control, namely fracture reduction and implant selection, on the biomechanical behavior of fracture fixation constructs. MATERIAL-METHODS: An experimental protocol was conducted with the use of instrumented sawbones, in order to validate the finite element models. The implants used were the Gamma3®and DHS systems. Subsequently, a series of scenaria were considered, including various reduction and implant angle combinations. Data were retrieved concerning the peak cancellous bone stresses around the hip screw and the volume of cancellous bone in the femoral head stressed at critical levels, as well as implant stresses and stresses on the cortical bone of the distal fragment. RESULTS: All stable fracture models displayed significantly decreased cancellous bone stresses and implant stresses compared to their unstable counterparts, regardless of implant used. The effect of increasing implant angle led to a decrease in implant stresses in all models studied, but had a beneficial effect on the stresses in the cancellous bone of the proximal fragment only in the subgroups of stable fractures with both implants and unstable fractures treated with a cephalomedullary nail (CMN). In unstable fractures anatomically reduced, the use of CMN led to significantly lower peak stresses in the cancellous bone and a smaller volume of bone stressed at critical levels. Increasing the reduction angle by 5 ° led to a significant decrease in both peak stresses and volume of bone stressed at critical levels, more prominent in the sliding hip screw (SHS) models. Decreasing the reduction angle into varus by 5 or 10 ° led to a significant increase in bone and implant stresses regardless of implant used. CONCLUSIONS: In stable two-part (AO31.A2) fractures the use of the SHS appears to be biomechanically equivalent to CMN. In unstable, anatomically reduced fractures, the use of CMN leads to significantly reduced cancellous bone stresses and decreased rotation of the proximal fragment during loading. A reduction in varus should be avoided at all costs. In unstable fractures treated with SHS a reduction in slight valgus appears to be biomechanically beneficial. The highest implant angle that allows for proper screw position and trajectory in the femoral head should be used for stable fractures with both implants and unstable fractures treated with Gamma3®.

Long-stemmed Hemiarthroplasty with Cerclage Wiring for the Treatment of Split-Head Fractures of the Proximal Humerus with Metaphyseal Extension: A Report of 2 Cases.

Introduction: Complex fractures of the proximal humerus with splitting-head component and metaphyseal propagation are very rare injuries that are difficult to treat. Preservation of the humeral head is always considered except in cases with severe comminution and compromised vascularity where shoulder hemiarthroplasty is an alternative option. Case Report: We present two male patients, 57- and 62-years-old who sustained such a complex proximal humeral fracture after a high-energy injury. They both managed with long-stemmed shoulder hemiarthroplasty and cerclage wiring of the metaphyseal area. They both demonstrated good clinical and radiological outcome at 32- and 24-months postoperatively. Conclusion: We report the functional and radiological outcomes of two cases of a rare proximal humeral fracture's pattern - combination of splitting-head and metaphyseal comminution - that were managed with long-stemmed hemiarthroplasty and cerclage wire and demonstrated good midterm clinical outcome.

Short-term clinical and radiological results of two different design metaphyseal fitting femoral stems in total hip arthroplasty: a prospective, randomized trial.

BACKGROUND: There is great design variability on short femoral stems available on the market. This study aims to evaluate the short-term clinical and radiological results of two different design short femoral stems, both classified as shortened tapered stems. METHODS: From March 2016 to March 2018, a prospective, randomized, parallel-group design study was conducted to compare functional and radiological outcomes of 45 patients underwent THA using the Tri-Lock Bone Preservation Stem and 45 patients underwent THA with the Minima S stem at a minimum 2 years of follow-up. Patients were assessed clinically and radiographically prior to surgery as well as at 3, 6, 12, and 24 months postoperatively. Primary outcomes were the change in health-related quality of life assessed with Western Ontario and McMaster Universities Osteoarthritis Index and 36-Item Short Form Health Survey and also the incidence of all hip-related complications. Secondary aims included hip function evaluated with the Harris hip score, rates of patient satisfaction, and the outcomes of a detailed radiological analysis. RESULTS: There were no significant differences between the 2 study groups in terms of patient-reported outcomes measurements, satisfaction scores, and complication rates at any of the measurement times. In both groups, stable fixation and radiographic osseointegration were achieved. However, analysis of the calcar region showed that 57.8% and 28.9% of patients had grade 1 or 2 stress shielding, in Tri-Lock and Minima S implantation group, respectively (p=0.015). Regarding coronal alignment, stems were placed in slight varus, valgus, and neutral position in 51.1%, 13.3%, and 35.6% of patients, respectively, in Tri-Lock BPS group. The Minima S stem was implanted at slight varus and valgus in 60% and 40% of patients, respectively, and neither stem in the exact neutral position. CONCLUSIONS: Both different design short femoral stems demonstrated excellent clinical performance at short-term follow up. Nevertheless, concerns were raised regarding the incidence of stress shielding phenomenon and mild discrepancies in coronal stem alignment during implantation. The clinical impact of these observations should be further evaluated through larger cohorts and longer follow-up. TRIAL REGISTRATION: ISRCTN registry, ISRCTN10096716 . Registered on May 8, 2018-Retrospectively registered.

Comparative analysis of the biomechanical behavior of two different design metaphyseal-fitting short stems using digital image correlation.

BACKGROUND: The progressive evolution in hip replacement research is directed to follow the principles of bone and soft tissue sparing surgery. Regarding hip implants, a renewed interest has been raised towards short uncemented femoral implants. A heterogeneous group of short stems have been designed with the aim to approximate initial, post-implantation bone strain to the preoperative levels in order to minimize the effects of stress shielding. This study aims to investigate the biomechanical properties of two distinctly designed femoral implants, the TRI-LOCK Bone Preservation Stem, a shortened conventional stem and the Minima S Femoral Stem, an even shorter and anatomically shaped stem, based on experiments and numerical simulations. Furthermore, finite element models of implant-bone constructs should be evaluated for their validity against mechanical tests wherever it is possible. In this work, the validation was performed via a direct comparison of the FE calculated strain fields with their experimental equivalents obtained using the digital image correlation technique. RESULTS: Design differences between Trilock BPS and Minima S femoral stems conditioned different strain pattern distributions. A distally shifting load distribution pattern as a result of implant insertion and also an obvious decrease of strain in the medial proximal aspect of the femur was noted for both stems. Strain changes induced after the implantation of the Trilock BPS stem at the lateral surface were greater compared to the non-implanted femur response, as opposed to those exhibited by the Minima S stem. Linear correlation analyses revealed a reasonable agreement between the numerical and experimental data in the majority of cases. CONCLUSION: The study findings support the use of DIC technique as a preclinical evaluation tool of the biomechanical behavior induced by different implants and also identify its potential for experimental FE model validation. Furthermore, a proximal stress-shielding effect was noted after the implantation of both short-stem designs. Design-specific variations in short stems were sufficient to produce dissimilar biomechanical behaviors, although their clinical implication must be investigated through comparative clinical studies.

Comparison of two metaphyseal-fitting (short) femoral stems in primary total hip arthroplasty: study protocol for a prospective randomized clinical trial with additional biomechanical testing and finite element analysis.

BACKGROUND: Total hip replacement has recently followed a progressive evolution towards principles of bone- and soft-tissue-sparing surgery. Regarding femoral implants, different stem designs have been developed as an alternative to conventional stems, and there is a renewed interest towards short versions of uncemented femoral implants. Based on both experimental testing and finite element modeling, the proposed study has been designed to compare the biomechanical properties and clinical performance of the newly introduced short-stem Minima S, for which clinical data are lacking with an older generation stem, the Trilock Bone Preservation Stem with an established performance record in short to midterm follow-up. METHODS/DESIGN: In the experimental study, the transmission of forces as measured by cortical surface-strain distribution in the proximal femur will be evaluated using digital image correlation (DIC), first on the non-implanted femur and then on the implanted stems. Finite element parametric models of the bone, the stem and their interface will be also developed. Finite element predictions of surface strains in implanted composite femurs, after being validated against biomechanical testing measurements, will be used to assist the comparison of the stems by deriving important data on the developed stress and strain fields, which cannot be measured through biomechanical testing. Finally, a prospective randomized comparative clinical study between these two stems will be also conducted to determine (1) their clinical performance up to 2 years' follow-up using clinical scores and gait analysis (2) stem fixation and remodeling using a detailed radiographic analysis and (3) incidence and types of complications. DISCUSSION: Our study would be the first that compares not only the clinical and radiological outcome but also the biomechanical properties of two differently designed femoral implants that are theoretically classified in the same main category of cervico-metaphyseal-diaphyseal short stems. We can hypothesize that even these subtle variations in geometric design between these two stems may create different loading characteristics and thus dissimilar biomechanical behaviors, which in turn could have an influence to their clinical performance. TRIAL REGISTRATION: International Standard Randomized Controlled Trial Number, ID: ISRCTN10096716 . Retrospectively registered on May 8 2018.

Osteolytic lesions (brown tumors) of primary hyperparathyroidism misdiagnosed as multifocal giant cell tumor of the distal ulna and radius: a case report.

BACKGROUND: Brown tumors represent a rare clinical manifestation reported in approximately 3% of patients with primary hyperparathyroidism and correspond to radiologically osteolytic lesions with well-defined borders in different parts of the skeleton. CASE PRESENTATION: We report the case of a 53-year-old white man who presented to our hospital with osteolytic lesions of his distal ulna and radius, causing pain and swelling of 2-month duration. A subsequent biopsy revealed histological features consistent with giant cell tumor and a complete resection of his distal ulna was followed, along with curettage and cementoplasty of the distal radial metaphysis. Two weeks later, he was re-admitted with diffuse musculoskeletal soreness, anorexia, constipation, nausea, and localized abdominal pain and multiple osteolytic lesions on plain radiographs. A histopathological examination of the ulna and radius specimens showed similar findings and, given the multifocality, brown tumors related to primary or secondary hyperparathyroidism was included in the differential diagnosis. A laboratory examination showed high total serum calcium (14.5 mg/dl) and low serum phosphorus and 25-hydroxyvitamin D levels. Primary hyperparathyroidism was suspected and confirmed by the elevated parathyroid hormone levels of 1453 pg/mL. At radiological work-up, using computed tomography, ultrasonography, and parathyroid subtraction technetium-99m sestamibi scintigraphy, a 4.5 × 2.5 × 3.2 cm mass emanating from the right lobe of his thyroid gland was detected, displaying extensive uptake in the right lower parathyroid gland. After appropriate medical support including hyperhydration and high doses of diuretics and diphosphonates, his laboratory profile normalized and he underwent total thyroidectomy with removal of the parathyroid glands. Our patient is now recovering 12 months after surgery, with normal values of serum parathyroid hormone and calcium levels. The lytic bone lesions have almost disappeared and no other additional orthopedic intervention was necessary. CONCLUSIONS: The present case report emphasizes the need of inclusion of brown tumors in the differential diagnosis of multifocal osteolytic bone lesions, in order to avoid harmful surgical interventions. Laboratory testing of serum phosphate, calcium levels, and parathyroid hormone levels should always be included in the routine survey of patients with multifocal osteolytic lesions.